Re: [IBMiOSS] RPG easier/harder to use than other languages?

John,

By the way, my day-to-day name is also john, my official name is jacobus,
and i already have a mail account "john..." so this email address is my
real name.

Cursors like you use with a sql result set, to iterate through the rows (or
in this case through the key/item pairs).

The keys are - of course - mutable. RPG (and this map impl) does not
replicate immutable data structures.

So we *shouldn't* mutate the keys, but what if we do anyway? Can the
tree become corrupted?

I think it's just like using a Java Map.
You can put any object in it as key as long as it supports the compareTo
method (defined at Object).

When you add a key/item pair the key will be inserted inbetween the other
keys in the right order.
This order won't change; it's fixed.
So if you change the key in some way which affects the sorting order, the
sorting order won't reflect the position in the map. So yes, then it's
corrupt. You just should not do that, the same with Java.




On Wed, Jul 5, 2017 at 6:52 PM, John Yeung <gallium.arsenide@xxxxxxxxx>
wrote:

On Wed, Jul 5, 2017 at 11:43 AM, jacobus erps <jacobus.erps@xxxxxxxxx>
wrote:

Interesting. This is not my idea of a map, then. If you have two
identical keys, does a lookup always find the same one? Or can it
sometimes find one but sometimes find the other? Or do you get both
values back on the same operation?

On a "get", by default you get the first one, but you can choose to get

the

last one if you want.
Of course, you can iterate over all dup keys, starting with the first one
(setll), or the last one.(setgt).

Now I understand what you mean by cursors, setll, and setgt.

I am still a little puzzled by this:

The keys are mutable ifd they're maps, thats true.
Once inserted into the map, you shouldn't mutate the keys, of course.

So we *shouldn't* mutate the keys, but what if we do anyway? Can the
tree become corrupted?

John Y.
--
This is the IBMi Open Source Roundtable (OpenSource) mailing list
To post a message email: OpenSource@xxxxxxxxxxxx
To subscribe, unsubscribe, or change list options,
visit: http://lists.midrange.com/mailman/listinfo/opensource
or email: OpenSource-request@xxxxxxxxxxxx
Before posting, please take a moment to review the archives
at http://archive.midrange.com/opensource.